System and Method for Controlling Evaporative Emissions

ABSTRACT

A system and method which implements a preferred embodiment of the present invention includes a pump control module for controlling evaporative emissions of engines. In one embodiment, fuel vapor is allowed to accumulate in an intake manifold for a first period of time after an engine is turned off. After the first period of time, the pump control module may open a vacant port and turn on a pump. The pump control module may run the pump for a second period of time. The second period of time may be determined based on the time needed to empty an estimated volume of accumulated fuel vapor from the intake manifold into one or more canisters, such as activated charcoal canisters. After the second period of time, the pump control module may decrease the running time and/or speed of the pump. When the engine is restarted, the vacant port may be closed, the pump may be turned off, and fuel vapor stored in the canisters may be controllably consumed via a purge valve mounted to the intake manifold. In one embodiment, a choke may be placed in between the vacant port and the canisters in order to reduce the number of canisters needed for a given pump size.

PRIORITY STATEMENT UNDER 35 U.S.C. §119 & 37 C.F.R. §1.78

This non-provisional patent application claims priority based upon prior U.S. Provisional Patent Application Ser. No. 61/362,480 filed Jul. 8, 2010 in the name of Martin Veinbergs entitled “System and Method for Controlling Evaporative Emissions,” the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The present invention relates generally to engine emissions and more particularly to evaporative engine emissions.

Automotive evaporative emissions are currently regulated by governmental environmental agencies, including both the United States Environmental Protection Agency and the California Air Resources Board. To reduce automotive evaporative emissions, fuel vapors may be collected into activate charcoal canisters when the automotive engine is turned off. The charcoal in the canisters absorbs the fuel vapor so as to store the fuel vapor in the canister and prevent it from being emitted to the atmosphere. When the engine is turned on, the absorbed fuel vapor is then pulled from the canisters into the engine and is consumed.

Evaporative emissions can be difficult to control if air mixes with the fuel vapor. If a significant amount of air is collected into an activated charcoal canister, for example, the air can reduce the charcoal's ability to absorb fuel vapor in the canister and thereby significantly reduce the capacity of the canister to hold fuel vapor. Consequently, a system and method is needed to collect fuel vapor into canisters while reducing the amount of air that may enter into the canisters.

Therefore, it can be appreciated that there is a significant need for an improved system and method for controlling evaporative emissions that can collect fuel vapor into canisters while reducing the amount of air that may enter into the canisters. Embodiments of the present invention can provide these and other advantages, as will be apparent from the following description and accompanying figure.

BRIEF SUMMARY

In accordance with one embodiment of the present invention, fuel vapor is allowed to accumulate in an intake manifold for a first period of time after an engine is turned off. After the first period of time, a pump control module may open a vacant port and turn on a pump. The pump control module may run the pump for a second period of time. The second period of time may be determined based on the time needed to empty an estimated volume of accumulated fuel vapor from the intake manifold into one or more canisters, such as activated charcoal canisters. After the second period of time, the pump control module may decrease the running time and/or speed of the pump. In one embodiment, the pump control module may be calibrated to modulate or cycle the pump at a 50% duty cycle. When the engine is restarted, the vacant port may be closed, the pump may be turned off, and fuel vapor stored in the canisters may be controllably consumed via a purge valve mounted to the intake manifold. In one embodiment, a choke may be placed in between the vacant port and the canisters in order to reduce the number of canisters needed for a given pump size.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic diagram of a system for controlling evaporative emissions in one embodiment of the present invention.

DETAILED DESCRIPTION

In one embodiment, the present invention comprises a system and method to collect fuel vapor from engines while reducing the amount of air that is able to mix with the fuel vapor as the fuel vapor is collected. The present invention may be used in connection with an engine with an unconventional fuel system, such as a liquefied petroleum gas fuel system, or with engines with other types of fuel systems, including gasoline fuel systems.

Reference is now made to FIG. 1, which is a schematic diagram of a system for controlling evaporative emissions in one embodiment of the present invention. In this embodiment, the intake manifold includes a purge valve 102 and a vacant port 105. The vacant port 105 may include an intake solenoid valve 104 to open and close the vacant port 105. The vacant port 105 may also connect via gas lines 110 b to one or more canisters such as a first canister 103 a and an optional second canister 103 b. The purge valve 102 may also connect via gas lines 110 a to the one or more canisters. The one or more canisters may be activated charcoal canisters or other types of canisters useful for trapping vapors. The one or more canisters may connect via gas lines 110 c to a pump 109 and via gas lines 110 c and gas line 110 d to a vent line 115. The vent line 115 may include a canister vent valve 107. The pump 109 may connect to a separate vent line 116. Those of ordinary skill in the art will understand that other embodiments of the present invention may include gas lines in different arrangements from those shown in FIG. 1.

The pump 109 may also connect via electrical lines 114 to a pump control module 106 and a battery 113, such as a 12 volt vehicle battery. The pump control module 106 may also connect via electrical lines 114 to an ignition switch 112, an engine control unit 111, the intake solenoid valve 104, and the canister vent valve 107. Those of ordinary skill in the art will understand that other embodiments of the present invention may include electrical lines in different arrangements from those shown in FIG. 1.

In one embodiment, when the ignition switch 112 is turned off, fuel vapor is allowed to accumulate in the intake manifold 101 for a first period of time. In one embodiment, the first period of time is set to approximately equal to twenty (20) minutes from the time that the vehicle ignition switch is turned off. In other embodiments, the length of the first period of time may be varied based on factors such as temperature, pressure, and/or fuel vapor concentrations, as may be measured in the intake manifold 101.

After the first period of time, the pump control module 106 may open the vacant port 105, such as by opening the intake solenoid valve 104, and turn on the pump 109. The pump control module 106 may run the pump 109 for a second period of time. The second period of time may be determined based on factors such as the time needed to empty an estimated volume of accumulated fuel vapor from the intake manifold 101 into the one or more canisters. Such a determination may correspond to factors such as the size of the intake manifold 101, the size of the pump 109, the capacity of the one or more canisters 103 a and 103 b, and/or other system parameters such as temperature, pressure, the capacity of the gas lines 110, and the system's resistance to vapor flow. In one embodiment, the second period of time is set to approximately equal to two (2) minutes from the time that the pump 109 is turned on. In other embodiments, the length of the second period of time may be varied based on factors such as temperature, pressure, and fuel vapor concentrations, as may be measured in the intake manifold 101, the gas lines 110, and/or the one or more canisters. For example, pressure sensor 108 may be used to measure pressure in gas line 110 d and relative pressure in the one or more canisters.

The pump 109, while running during the second period of time, may pull vapor from the canisters through gas lines 110 c and to vent line 116. As a result, the pressure in the canisters will be reduced. This reduction in pressure may cause the fuel vapor that has accumulated in the intake manifold 101 to travel from the intake manifold 101, through the vacant port 105, and into the one or more canisters via the gas lines 110 b.

After the second period of time, or once a majority of the fuel vapor that has accumulated in the intake manifold 101 has left the intake manifold 101, the pump control module 106 may stop or decrease the running time and/or speed of the pump 109. Otherwise, the pump 109 might, for example, begin to draw significant amounts of air from the intake manifold 101 into the one or more canisters. In one embodiment, the pump control module 106 may be calibrated to modulate or cycle the pump 109 at a fifty percent (50%) duty cycle after the end of the second period of time. For example, the pump control module 106 may, for repeating cycles, turn off the pump 109 and close the vacant port 105 for approximately one (1) minute and then turn on the pump 109 and open the vacant port 105 for approximately one (1) minute. After the end of the second period of time, the pump 109 may continue to run at a fifty percent (50%) duty cycle until the ignition switch 112 is turned on. When the ignition switch 112 is turned on, the vacant port 105 may be closed and the pump 109 may be turned off. The fuel vapor stored in the one or more canisters may then be controllably consumed via a purge valve 102 mounted to the intake manifold 101 and the gas lines 110 a.

In addition, a choke (not shown) may be placed in between the vacant port 105 and the one or more canisters in order to reduce the number of the one or more canisters needed for a pump 109 of a given size. In one embodiment, the system and method may include two canisters and no choke. In another embodiment, the system and method may include a choke and a single canister.

While the present system and method has been disclosed according to the preferred embodiment of the invention, those of ordinary skill in the art will understand that other embodiments have also been enabled. Even though the foregoing discussion has focused on particular embodiments, it is understood that other configurations are contemplated. In particular, even though the expressions “in one embodiment” or “in another embodiment” are used herein, these phrases are meant to generally reference embodiment possibilities and are not intended to limit the invention to those particular embodiment configurations. These terms may reference the same or different embodiments, and unless indicated otherwise, are combinable into aggregate embodiments. The terms “a”, “an” and “the” mean “one or more” unless expressly specified otherwise.

When a single embodiment is described herein, it will be readily apparent that more than one embodiment may be used in place of a single embodiment. Similarly, where more than one embodiment is described herein, it will be readily apparent that a single embodiment may be substituted for that one device.

In light of the wide variety of possible devices and methods for controlling evaporative engine emissions, the detailed embodiments are intended to be illustrative only and should not be taken as limiting the scope of the invention. Rather, what is claimed as the invention is all such modifications as may come within the spirit and scope of the following claims and equivalents thereto.

None of the descriptions in this specification should be read as implying that any particular element, step or function is an essential element which must be included in the claim scope. The scope of the patented subject matter is defined only by the allowed claims and their equivalents. Unless explicitly recited, other aspects of the present invention as described in this specification do not limit the scope of the claims. 

1. A system for controlling evaporative engine emissions comprising: an intake manifold including a vacant port which connects to one or more canisters, a pump which connects to said one or more canisters, and a pump control module configured to run said pump after a first period of time.
 2. The system of claim 1 wherein the length of said first period of time is approximately twenty minutes from the time that an ignition switch is turned off.
 3. The system of claim 1 wherein the length of said first period of time is varied based on one or more of the following variables measured at said intake manifold: temperature, pressure and fuel vapor concentration.
 4. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time.
 5. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time approximately two minutes.
 6. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time is varied based on one or more of the following variables measured at said intake manifold, said one or more canisters or a gas line connecting to said one or more canisters: temperature, pressure, and fuel vapor concentration.
 7. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time is determined based on one or more of the following factors: the size of said intake manifold, the size of said pump, the capacity of said one or more canisters, temperature, pressure, the capacity of a gas line, and the resistance to vapor flow of a gas line.
 8. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to run said pump at a decreased rate after said second period of time.
 9. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to modulate or cycle said pump after said second period of time.
 10. The system of claim 1 wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to run said pump at approximately a fifty percent duty cycle after said second period of time.
 11. The system of claim 1 wherein, after an ignition switch is turned on, fuel vapor stored in said one or more canisters is consumed via a purge valve mounted to said intake manifold.
 12. The system of claim 1 further comprising a choke between said vacant port and said one or more canisters.
 13. A method for controlling evaporative engine emissions comprising: after a first period of time, running a pump for a second period of time wherein said pump is connected to one or more canisters and said one or more canisters are connected to a vacant port of an intake manifold.
 14. The method of claim 13, wherein the length of said first period of time is approximately twenty minutes from the time that said ignition switch is turned off.
 15. The method of claim 13 wherein the length of said first period of time is varied based on one or more of the following variables measured at said intake manifold: temperature, pressure and fuel vapor concentration.
 16. The method of claim 13 wherein said pump is connected to a pump control module configured to start said pump.
 17. The method of claim 13 wherein the length of said second period of time approximately two minutes.
 18. The method of claim 13 wherein the length of said second period of time is varied based on one or more of the following variables measured at said intake manifold, said one or more canisters or a gas line connecting to said one or more canisters: temperature, pressure, and fuel vapor concentration.
 19. The method of claim 13 further comprising running said pump at a decreased rate after said second period of time.
 20. The method of claim 13 further comprising modulating or cycling said pump after said second period of time.
 21. The method of claim 13 further comprising running said pump at approximately a fifty percent duty cycle after said second period of time.
 22. The method of claim 13 wherein, after an ignition switch is turned on, fuel vapor stored in said one or more canisters is consumed via a purge valve mounted to said intake manifold.
 23. The method of claim 13 wherein a choke is located between said vacant port and said one or more canisters.
 24. The method of claim 13 further comprising determining the length of said second period of time based on one or more of the following factors: the size of said intake manifold, the size of said pump, the capacity of said one or more canisters, temperature, pressure, the capacity of a gas line, and the resistance to vapor flow of a gas line. 